178 



Cincinnati Society of Natural History. 



THE NERVOUS SYSTEM. 

 By A. J. Howe, M. D. 



The Fly-trap of Venus and a few other plants, when gently touched, 

 as by the alighting of an insect, display responsive movements as if 

 to capture prey. The reflex action thus manifested does not prove 

 that such energies come through the agency of a nervous system, but 

 simply demonstrates that the vegetable fibre of certain plants is irri- 

 table or impressible to a responsive degree. The white lily of our 

 ponds displays its delicate and odorous petals at night and in cloudy 

 weather; and the heliotrope, as the name implies, turns with the sun; 

 but there is no neural cell or nerve tubule in these interesting flowers. 



Nerves are peculiar to animals. The stupid slug and the larval 

 worm have two varieties of neurine in their composition; and these 

 are displa3 7 ed in groups of cells (ganglia), and plexuses of threads. 

 The former corresponds to the "gray" matter of true brain, and the 

 latter to the " white" or tubular neurine. The vesicles to be found in 

 neural knots, nodules, ganglia or "centers," are soft, fatty and albu- 

 minous, with a perceptible admixture of phosphorus. Functional 

 activity is kept up in these ganglionic bodies by the presence of 0x3- 

 gen, which is furnished through a circulating medium; for instance, 

 the blood in elevated animal forms. Nervous energy is developed in 

 ganglia as certainly as secretions come from glands. 



A remarkable quality of neural endowment is, that the nervous sys- 

 tem acts intelligently in the way of protecting the individual. The 

 nervous filaments in the skin of an earth-worm warn the creature, as 

 drouth approaches, to descend to planes where moisture is plentiful, 

 and to return to the surface when warm rains render shallower planes 

 agreeable. The lowly organism has no special senses, yet common 

 cutaneous sensation does for all its needs. 



The spider has no brain, } T et a few neural nodules and commissural 

 filaments excellently serve the creature. It manifests discrimination 

 in the selection of a place in which nets may be profitabl} T spread; 

 it seemingly knows where game is plentiful, and removes to better 

 grounds when the supply is exhausted. As a strategist, the spider 

 has no equal among insects. The ant and the bee exhibit great in- 

 stinctive wisdom, yet they do not know enough to patiently lie in wait 

 that they may suddenly pounce upon unsuspecting victims. 



Fishes and reptiles possess a low order of brains, and rather feeble 

 instincts, except at certain seasons. The stickleback builds a nest 



